1. Field of the Invention
The present invention relates to memory devices, and more specifically to a shared memory device that mediates mutual communication among a plurality of CPUs.
2. Description of the Background Art
Japanese Patent Application Laid-Open No. 2001-166960 discloses a multiprocessor system in which an individual memory of each processor module in the multiprocessor system is allocated as an individual area in a shared memory that is shared by the processor modules.
Techniques pertinent to the present invention are also disclosed in Japanese Patent Application Laid-Open Nos. 2000-347927, 10-171750 (1998), and 2001-157049.
In some network, a plurality of PCs communicate via a shared memory. However, response speed required is slow with network communication among PCs compared to communication among CPUs in a device. This means that problems can occur when a shared memory in network communication is used for communication among PCs.
In addition, it has been desired to increase reliability of a memory device used for mutual communication among a plurality of CPUs via a memory shared by the plurality of CPUs and an individual memory provided with each of the CPUs.